Organic electroluminescent device

ABSTRACT

Disclosed is an organic electroluminescent (EL) device for enhancing the luminous efficiency. A first electrode is formed on a substrate. A CVD insulating film of low dielectric constant having an opening exposing the first electrode is formed on the first electrode and the substrate. An organic EL layer and a second electrode are sequentially stacked on the opening. A wall surrounding a region of the organic EL layer is formed of the CVD insulating film of low dielectric constant, the surface treatment of the pixel electrode can be performed using O2 plasma enhance luminance properties.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national phase application of PCT/KR02/02418 filedon Dec. 24, 2002, and claims priority thereto under 35 USC 371.PCT/KR02/02418, in turn, claims priority from Korean Application No.10-2002-0033326 filed on Jun. 14, 2002, the content of which isincorporated by reference herein in its entirety.

Technical Field

The present invention relates to an organic electroluminescent (EL)device, and more particularly, to an organic EL device in which a CVDinsulating film of low dielectric constant is used to enhance theluminous efficiency.

Background Art

In the information society of these days, electronic display devices aremore important as information transmission media and various electronicdisplay devices are widely applied for industrial apparatus or homeappliances. Such electronic display devices are being continuouslyimproved to have new appropriate functions for various demands of theinformation society.

In general, electronic display devices display and transmit variouspieces of information to users who utilize such information. That is,the electronic display devices convert electric information signalsoutputted from electronic apparatus into light information signalsrecognized by users through their eyes.

In the electronic display devices dividing into an emissive displaydevice and a non-emissive display device, the emissive display devicedisplays light information signals through a light emission phenomenathereof and the non-emissive display device displays the lightinformation signals through a reflection, a scattering or aninterference thereof. The emissive display device includes a cathode raytube (CRT), a plasma display panel (PDP), a light emitting diode (LED)and an electroluminescent display (ELD). The emissive display device iscalled as an active display device. Also, the non-emissive displaydevice, called as a passive display device, includes a liquid crystaldisplay (LCD), an electrochemical display (ECD) and an electrophoreticimage display (EPID).

The CRT has been used for a television receiver or a monitor of acomputer as the display device for a long time since it has a highquality and a low manufacturing cost. The CRT, however, has somedisadvantages such as a heavy weight, a large volume and high powerconsumption.

Recently, the demand for a new electronic display device is greatlyincreased such as a flat panel display device having excellentcharacteristics that thin thickness, light weight, low driving voltageand low power consumption. Such flat panel display devices may bemanufactured according to the rapidly improved semiconductor technology.

An electroluminescent (EL) device is attracting attention of interestedperson as one of the flat panel displays. The EL device is generallydivided into an inorganic EL device and an organic EL device dependingon used materials.

The inorganic EL device is a display in which a high electric field isapplied to a light emitting part and electrons are accelerated in theapplied high electric field to be collided with a light emitting center,thereby exciting the light emitting center to emit light.

The organic EL device is a display in which electrons and holes areinjected into a light emitting part from cathode and anode,respectively, and the injected electrons and holes are combined witheach other to generate excitons, thereby emitting light when theseexcitons are transited from an excited state to a base state.

Owing to the above operation mechanism, the inorganic EL device needs ahigh driving voltage of 100-200 V, whereas the organic EL deviceoperates at a low voltage of 5-20 V The above advantage of the organicEL device is activating researches on the organic ELD. Also, the organicEL device has superior properties such as wide viewing angle, highresponse speed, high contrast and the like.

The organic EL device includes a plurality of organic EL elements (i.e.,pixels) suitable for display purposes such as monochrome or multi-colordisplay, still image display, segmented display, passive or active typematrix display, etc.

The active matrix organic EL device is a display that independentlydrives EL elements corresponding to a plurality of pixels usingswitching elements such as a thin film transistor. The organic EL deviceis also referred to as an organic electroluminescent display (OELD) oran organic light emitting device (OLED).

In an active matrix type organic EL device, thin film transistors areformed on a transparent insulating substrate, each of the thin filmtransistors having an active pattern, a gate electrode and source/drainelectrodes. With via holes exposing any one electrode of thesource/drain electrodes, e.g., the drain electrode, a passivation layeris formed on the entire surface of the substrate including the thin filmtransistors.

Upon the passivation layer, there are formed pixel electrodes connectedto the drain electrodes of the thin film transistors through the viaholes. The pixel electrodes consisting of a transparent conductivematerial such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO) areprovided as an anode injecting holes.

On the passivation layer including the pixel electrodes, there is formedan insulating layer having openings exposing a portion of the pixelelectrodes. Organic EL layers are formed on the openings. A metalelectrode for a cathode is formed on the organic EL layers.

The insulating layer serves as a wall or a bank layer surrounding aregion where the organic EL layer is formed. The wall plays a role ofpreventing the EL layers and the layers of the non-pixel region frombeing in contact with a shadow mask, when the shadow mask is shifted tosuccessively form red (R), green (G) and blue (B) EL layers. Further,the wall is provided to reduce a coupling capacitance between the pixeland cathode electrodes.

According to a conventional organic EL device, the wall is formed of ahigh polymeric organic insulating film, e.g., imide or acryl basedorganic insulating film. However, When the metal electrode is formedabove the organic insulating film, the lifting of the metal electrodemay be caused due to a poor adhesion of the organic insulating film.

The surface treatment process of the pixel electrode for enhancing theluminance efficiency, e.g., O₂ plasma treatment, cannot be utilized.This is because the high polymers of the organic insulating film areeasily damaged due to the plasma. That is, when the surface treatment ofthe plasma electrode is performed using O₂ plasma, the surface of thewall is damaged so that the organic insulating film is coated on thecontact region to increase a contact resistance and deteriorate thedevice performance. Accordingly, in case that the wall is formed of theorganic insulating film, the surface treatment process of the pixelelectrode cannot be used to thereby deteriorate luminance properties ofthe organic EL element.

Since the organic EL element may be deteriorated due to minute moisturecontent of the high polymers when driving the element, an additionalheat treatment process may be demanded.

DISCLOSURE OF THE INVENTION

Accordingly, it is an object of the present invention to provide anorganic EL device in which luminance properties can be enhanced.

In order to accomplish the above object, the present invention providesan organic EL device comprising a substrate; a first electrode formed onthe substrate; a CVD insulating film of low dielectric constant formedon the first electrode and the substrate in order to suppress theformation of a coupling capacitance, the CVD insulating film having anopening exposing the first electrode; an organic EL layer formed on theopening; and a second electrode formed on the organic EL layer.

Preferably, the CVD insulating film of low dielectric constant iscomprised of SiOC and has a dielectric constant of 3.5 and less. The CVDinsulating film of low dielectric constant is formed to a thickness of 1um or more.

Further, in an organic EL device of the present invention, thin filmtransistors are formed on a substrate, each of the thin film transistorshaving an active pattern, a gate insulating film, a gate electrode andsource/drain electrodes. A passivation layer is formed on the thin filmtransistors and the substrate. Pixel electrodes are formed on thepassivation layer so as to be connected to the thin film transistors. ACVD insulating film of low dielectric constant having openings exposingeach of the pixel electrodes is formed on the pixel electrodes and thepassivation layer. Organic EL layers are formed on each of the openings.A metal electrode is formed on the organic EL layers and the CVDinsulating film of low dielectric constant.

In addition, the present invention provides an organic EL devicecomprising a substrate; first electrodes in a form of stripe formed onthe substrate; a CVD insulating layer having openings formed on thefirst electrodes and the substrate, the opening being formed to have atapered slope; organic EL layers formed on each of the openings; andsecond electrodes in a form of stripe formed on the organic EL layers,the first and second electrodes being arranged to cross each other.

According to the present invention, a wall surrounding a region wherethe organic EL layer is formed is comprised of a CVD insulating film oflow dielectric constant. Since the surface of the CVD insulating film oflow dielectric constant is not damaged due to plasma, the surfacetreatment of the pixel electrode is performed using O2 plasma to therebyenhance the luminous efficiency and the luminance properties.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and other advantages of the present invention willbecome more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a cross-sectional view of an active matrix type organic ELdevice in accordance with a first embodiment of the present invention;

FIGS. 2A to 2F are cross-sectional views illustrating a method ofmanufacturing the AMOLED shown in FIG. 1;

FIG. 3 is a cross-sectional view of a passive matrix type organic ELdevice in accordance with a second embodiment of the present invention;

FIG. 4 is a graph showing voltage-current characteristic of the organicEL device in accordance with the present invention;

FIG. 5 is a graph showing luminance-voltage characteristic of theorganic EL device in accordance with present invention; and

FIG. 6 is a graph showing luminance-current characteristic of theorganic EL device in accordance with the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, exemplary embodiments of the present invention will be described indetail with reference to the attached drawings.

FIG. 1 is a cross-sectional view of an active matrix type organic ELdevice in accordance with a first embodiment of the present invention.

Referring to FIG. 1, a blocking layer 102 comprised of silicon oxide isformed on the entire surface of a transparent insulating substrate 100such as glass, quartz, or sapphire. The blocking layer 102 may beskipped, but it is preferred to form the blocking layer 102 in order toprevent impurities in the substrate 100 penetrating into a silicon filmduring a subsequent crystallization process for an amorphous siliconfilm.

On the blocking layer 102, there are formed thin film transistors 120.The thin film transistor 120 includes an active pattern 104, a gateelectrode 108 and source/drain electrode 116 and 118. Specifically,polycrystalline active patterns 104 are formed on the blocking layer102. A gate insulating film 106 comprised of silicon nitride or siliconoxide is formed on the active patterns 104 and the blocking layer 102.Gate electrodes 108 are formed on the gate insulating film 106, the gateelectrode 108 being across each of the active patterns 104 to definesource/drain regions 105S and 105 ad and a channel region 105C. That is,an intersection where the active pattern 104 is overlapped with the gateelectrode 108 becomes a channel region 105C. The active pattern 104 isdivided into two portions by the channel region 105C. One portion of theactive pattern 104 becomes the source region 105S, and the other portionthereof is the drain region 105D. At this time, the location of thesource region 105S and the drain region 105D may be changed.

An interlayer insulating film 110 comprised of an inorganic insulatingmaterial such as silicon oxide (SiO₂) or silicon nitride (Si₃N₄) isformed on the gate electrodes 108 and the gate insulating film 106.

Upon the interlayer insulating film 110, there are formed source/drainelectrodes 116 and 118 connected to the source/drain regions 105S and105D of the active pattern 104 through contact holes 112 and 114,respectively.

A passivation layer 122 comprised of an inorganic insulating materialsuch as silicon nitride or an acryl based photosensitive organicinsulating material is formed on the source/drain electrodes 116 and 118and the interlayer insulating film 110.

Upon the passivation layer 122, there are formed pixel electrodes 126connected with any one electrode of the source/drain electrodes 116 and118, for example, the drain electrode 118, through via holes 124. Thepixel electrode 126 comprised of a transparent conductive material suchas ITO or IZO is provided as an anode of an organic EL element.

On the passivation layer 122 including the pixel electrodes 126, a CVDinsulating film 128 of low dielectric constant is formed having openings130 exposing a portion of the pixel electrodes 126. Red, green and blueorganic EL layers 132R and 132G are formed on each of the opening 130.As a cathode of the organic EL element, a metal electrode 134 is formedon the organic EL layers 132R and 132G.

The organic EL layer consists of at least one organic film. That is, theorganic EL layer is formed by sequentially stacking a hole injectionlayer (HIL), a hole transfer layer (HTL), an emission layer (EML), anelectron transfer layer (ETL) and an electron injection layer (EIL).Here, the EML includes red, green and blue emission layers.

In the active matrix type organic EL device, each of the pixels aredriven by signals applied to the gate electrode and the source/drainelectrodes of the switching thin film transistor, so that the metalelectrode 134 is formed to a common electrode.

The CVD insulating film 128 of low dielectric constant serves as a wallsurrounding a region where the organic EL layer is formed. Further, theCVD insulating film 128 of low dielectric constant plays a role ofpreventing the EL layers and the layers of the non-pixel region frombeing in contact with a shadow mask, when the shadow mask is shifted tosuccessively form red (R), green (G) and blue (B) EL layers.

According to the prevent invention, the CVD insulating film 128 of lowdielectric constant is formed of SiOC film having a dielectric constantbelow 3.5 in order to suppress (or reduce) the formation of a couplingcapacitance between the pixel electrode 126 and the metal electrode 134.The CVD insulating film 128 of low dielectric constant is formed to athickness of 1 um or more in order, to secure a vertical intervalbetween the pixel electrode 126 and the metal electrode 134. Further, itis preferred that the CVD insulating film 128 of low dielectric constantis overlapped to more than 1 um with the edge portion of the pixelelectrode 126 in order to secure alignment margin of the organic ELlayer.

In general, the lifting of the metal electrode 134 is not caused abovethe CVD insulating film 128 of low dielectric constant because a CVDfilm has good adhesion to the other films and superior step coverage.Further, since the surface of the CVD film is not damaged due to plasma,the wall is formed of the CVD insulating film 128 of low dielectricconstant to thereby perform the surface treatment of the pixel electrode126 using O₂ plasma. Accordingly, the luminous efficiency and theluminance properties can be enhanced without damaging the wall.

Further, since a CVD film has lower hydroscopicity and higher thermalresistance than those of an organic film, the deterioration of elementis not caused when driving the organic EL element.

In case that an inorganic insulating film of low dielectric constant isdeposited by a plasma-enhanced chemical vapor deposition (PECVD) methodto form the wall, the dielectric constant can be more decreased bycontrolling the deposition conditions. Accordingly, the wall can beformed to a thin thickness, thereby reducing the verticalstep-difference and increasing a process margin.

FIGS. 2A to 2F are cross-sectional views for illustrating a method ofmanufacturing the organic EL device shown in FIG. 1.

Referring to FIG. 2A, on the entire surface of a transparent insulatingsubstrate 100 such as glass, quartz or sapphire, a silicon oxide isdeposited to a thickness of about 1000 A by a PECVD method to form ablocking layer 102. The blocking layer 102 plays a role of preventingimpurities in the substrate 100 from being penetrated into a siliconfilm during a subsequent crystallization process for an amorphoussilicon film.

Upon the blocking layer 102, an amorphous silicon film is deposited to athickness of about 500 A by LPCVD or PECVD method to form an activelayer. A laser annealing is carried out to crystallize the active layerinto the polycrystalline silicon layer. Then, the polycrystallinesilicon layer is patterned through a photolithography process to form anactive pattern 104 on a thin film transistor region within a unit pixel.

Thereafter, on the active pattern 104 and the blocking layer 102, asilicon oxide is deposited to a thickness of about 1,000-2,000 Å by thePECVD to form a gate insulating film 106. A gate layer, e.g., a singlemetal layer containing aluminum (Al) such as Al, AlNd, etc, or amulti-metal layer in which an Al alloy is stacked on chrome (Cr) ormolybdenum (Mo) alloy, is deposited and patterned by a photolithographyprocess. As a result, there are formed a gate line (not shown) extendingin a first direction and a gate electrode 108 of the thin filmtransistor branched from the gate line.

Here, impurity ions are implanted using a photo mask used for patterningthe gate layer to thereby form source/drain regions 105S and 105D in thesurface on both sides of the active pattern 104. During the source/drainimplantation, the gate electrode 108 blocks the impurity ions to definea channel region 105C in the active pattern 104 located thereunder.

Referring to FIG. 2B, laser or furnace annealing is performed in orderto activate the doped ions of the source/drain regions and to cure thedamage of the silicon layer. Then, a silicon nitride is deposited to athickness of approximately 800 Å on the entire surface of the resultantstructure to form an interlayer insulating film 110.

Thereafter, the interlayer insulating film 110 is etched away through aphotolithography process to form contact holes 112 and 114 exposing thesource/drain regions 105S and 105D. A data layer, e.g., MoW or AlNd, isdeposited on the interlayer insulating film 110 and the contact holes112 and 114 to a thickness of approximately 3,000-6,000 Å, and then,patterned by a photolithography process. By doing so, there are formed adata line (not shown) extending in a second direction perpendicular tothe first direction, a direct current signal line (Vdd) and source/drainelectrodes 116 and 118 respectively connected to the source/drainregions 105S and 105D through the contact holes 112 and 114.

Through the aforementioned processes, there are formed thin filmtransistors 120 including the active pattern 104, the gate insulatingfilm 106, the gate electrode 108 and the source/drain electrodes 116 and118.

Referring to FIG. 2C, on the interlayer insulating film 110 includingthe thin film transistors 120, a silicon nitride is deposited to athickness of approximately 2,000-3,000 Å to form a passivation layer122. Then, the passivation layer 122 is etched away using aphotolithography process to form via holes 124 exposing any one of thesource electrode 116 and the drain electrode 118, for example, the drainelectrodes 118.

A transparent conductive film such as ITO or IZO is deposited on thepassivation layer 122 and the via holes 124, and then, patterned by aphotolithography process to form pixel electrodes 126 connected to thedrain electrodes 118 of the thin film transistors 120 through the viaholes 124. The pixel electrode 126 is provided as an anode of an organicEL element.

Referring to FIG. 2D, a CVD insulating film 128 of low dielectricconstant less than 3.5, e.g., SiOC film, is deposited on the pixelelectrodes 126 and the passivation layer 122, and then, patterned by aphotolithography process to form openings 130 exposing a portion of thepixel electrodes 126.

Then, in order to enhance luminance properties of the organic ELelement, a surface treatment of the pixel electrode 126 is carried outusing O₂ plasma.

Referring to FIG. 2E, after locating a shadow mask 135 above the CVDinsulating film 128 of low dielectric constant having the openings 130,a red organic EL layer 132R is formed.

Referring to FIG. 2F, the shadow mask 135 is shifted to form a greenorganic EL layer 132G. Then, though not shown, the shadow mask 135 isshifted again to thereby form a blue organic EL layer.

After successively forming the red, green and blue organic EL layers asdescribed above, a metal electrode 134 serving as a cathode of theorganic EL element is formed on the entire surface of the resultantstructure.

FIG. 3 is a cross-sectional view of a passive matrix type organic ELdevice in accordance with a second embodiment of the present invention.

Referring to FIG. 3, first electrodes (i.e., anode electrodes) 210comprised of a transparent conductive film such as ITO are formed on atransparent insulating substrate 200 such as glass, quartz or sapphire.The first electrodes 210 are formed in a shape of stripe extending afirst direction.

Having openings 240 exposing each of the first electrodes 210, a CVDinsulating film 218 of low dielectric constant, e.g., SiOC film isformed on the first electrodes 210 and the substrate 200. Preferably,the CVD insulating film 218 of low dielectric constant has a dielectricconstant below 3.5 in order to suppress the formation of a couplingcapacitance between the first electrode 210 and a second electrode for acathode, and is formed to a thickness of 1 um or more.

The CVD insulating film 218 of low dielectric constant serves as a wallsurrounding a region where the organic EL layer is formed and separatesthe second electrode by the unit pixel. Further, the CVD insulating film218 of low dielectric constant plays a role of preventing the EL layersand the layers of the non-pixel region from being in contact with ashadow mask, when the shadow mask is shifted to successively form red(R), green (G) and blue (B) EL layers.

Preferably, the CVD insulating film 218 of low dielectric constant ispatterned so as to have an inverse tapered slope. Accordingly, theopening 240 exposing the first electrode 210 is formed with a taperedslope.

Between the first electrode 210 and the CVD insulating film 218 of lowdielectric constant, an insulating layer 215 is formed in order to coverthe edge portion of the first electrode 210. That is, the insulatinglayer 215 plays a role of preventing organic EL layers from beingdeposited on the stepped portion of the first electrode 210.

Red, green and blue organic EL layers 220 R, 220G and 220B are formed oneach of the openings 240. On the organic EL layers 220R, 220G and 220B,there is formed the second electrode 225 in a form of stripe extending asecond direction perpendicular to the first direction. Accordingly, thecross part of the first and second electrodes 210 and 225 becomes a unitpixel region.

The organic EL layers 220R, 220G and 220B includes more than one layer;a hole injection layer (HIL), a hole transfer layer (HTL), an emissionlayer (EML), an electron transfer layer (ETL) and an electron injectionlayer (EIL).

The second electrode 225 should be separated by the unit pixel in orderto apply an individual signal to each of the pixels because no switchingelement for driving each of the pixels is formed in the passive matrixtype organic EL device. Therefore, if the CVD insulating film 218 of lowdielectric constant is formed to have an inverse tapered slope, thesecond electrode 225 is deposited only on the top of the CVD insulatingfilm 218 of low dielectric constant and the bottom of the opening 240,excluding the sidewalls of the opening 240 having a tapered slope. As aresult, the second electrode 225 is simultaneously separated by the unitpixel during the deposition of the second electrode 225.

In a conventional passive matrix type organic EL device, a highpolymeric organic insulating film of low dielectric constant is used asthe separator of the second electrode and the wall. Accordingly, O₂plasma treatment of the first electrode 210 for increasing the luminousefficiency cannot be performed because the high polymers of the organicinsulating film are easily damaged due to the plasma.

On the contrary, in the passive matrix type organic EL device of thepresent invention, the CVD insulating film of low dielectric constant isused as the separator of the second electrode and the wall, so that thesurface treatment of the first electrode 210 is performed using O₂plasma to thereby enhance the luminous efficiency of the organic ELelement.

Further, the lifting of the second electrode 225 is not generatedbecause the CVD insulating film 218 of low dielectric constant has goodadhesion to the other films. In addition, when driving the organic ELelement, the element is not deteriorated because the CVD insulating film218 of low dielectric constant has lower hydroscopicity and higherthermal resistance than those of an organic film.

FIG. 4 is a graph showing voltage-current characteristic of the organicEL device in accordance with the present invention. In graph, a symbol ⋄indicates a case where only the first electrode comprised of ITO isformed on the entire surface of the transparent insulating substrate. Asymbol ▪ indicates a case where the surface of the first electrode is O₂plasma-treated. A symbol ▴ indicates a case where the CVD insulatingfilm of low dielectric constant, e.g., SiOC film is deposited on thefirst electrode. A symbol x indicates a case where the surface of thefirst electrode is O₂ plasma-treated after the SiOC film is deposited.

Referring to FIG. 4, in the case (▴) where the CVD insulating film oflow dielectric constant, e.g., SiOC film was deposited on the firstelectrode comprised of ITO, the voltage-current characteristic was moredeteriorated than the case (⋄) of forming only first electrode. However,in the case (x) where the O₂ plasma treatment was performed afterdepositing the SiOC film, the voltage-current characteristic wasenhanced to the same level as that of the case (▪) where the O₂ plasmatreatment was performed to the substrate on which only first electrodeis formed.

FIG. 5 is a graph showing luminance-voltage characteristic of theorganic EL device in accordance with the present invention. In graph, asymbol ⋄ indicates a case where only the first electrode comprised ofITO was formed on the entire surface of the transparent insulatingsubstrate. A symbol ▪ indicates a case where the surface of the firstelectrode is O₂ plasma-treated. A symbol ▴ indicates a case where theCVD insulating film of low dielectric constant, e.g., SiOC film isdeposited on the first electrode. A symbol x indicates a case where thesurface of the first electrode is O₂ plasma-treated after the SiOC filmis deposited.

Referring to FIG. 5, in the case (▴) where the CVD insulating film oflow dielectric constant, e.g., SiOC film was deposited on the firstelectrode comprised of ITO (case ▴), the luminance-voltagecharacteristic was more deteriorated than the case (⋄) of forming onlyfirst electrode. However, in the case (x) where the O₂ plasma treatmentwas performed after depositing the SiOC film (case x), theluminance-voltage characteristic was enhanced to the same level as thatof the case (▪) where the O₂ plasma treatment was performed to thesubstrate on which only first electrode is formed.

FIG. 6 is a graph showing luminance-current characteristic of theorganic EL device in accordance with the present invention. In graph, asymbol ⋄ indicates a case where only the first electrode comprised ofITO is formed on the entire surface of the transparent insulatingsubstrate. A symbol ▪ indicates a case where the surface of the firstelectrode is O₂ plasma-treated. A symbol ▴ indicates a case where theCVD insulating film of low dielectric constant, e.g., SiOC film isdeposited on the first electrode. A symbol x indicates a case where thesurface of the first electrode is O₂ plasma-treated after the SiOC filmis deposited.

Referring to FIG. 6, in the case (x) where the SiOC film was depositedon the first electrode and the O₂ plasma treatment was carried out, itwas obtained the superior luminance-current characteristic as comparedto the case (▪) where the O₂ plasma treatment was performed to thesubstrate on which only first electrode is formed.

According to the present invention as described above, a wallsurrounding a region of an organic EL layer is comprised of a CVDinsulating film of low dielectric constant. Since the surface of the CVDinsulating film of low dielectric constant is not damaged due to plasma,the surface treatment of the pixel electrode is performed using O₂plasma to thereby enhance the luminous efficiency and the luminanceproperties.

Further, the CVD insulating film of low dielectric constant having goodadhesion and step coverage is utilized to cause no lifting of a metalelectrode (i.e., second electrode). In addition, when driving theorganic EL element, the element is not deteriorated because the CVDinsulating film 218 of low dielectric constant has lower hydroscopicityand higher thermal resistance than those of an organic film.

While the present invention has been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade hereto without departing from the spirit and scope of the inventionas defined by the appended claims.

1. An organic electroluminescent device comprising: a substrate; a thinfilm transistor formed on the substrate; a first electrode electricallycoupled to the thin film transistor and having a surface treated byoxygen plasma; a chemical vapor deposition insulating film formed on thefirst electrode and the substrate, the chemical vapor deposition filmhaving an opening portion extending to the first electrode; an organicelectroluminescent layer formed in the opening portion; and a secondelectrode formed on the organic electroluminescent layer.
 2. The deviceas claimed in claim 1, wherein the chemical vapor deposition insulatingfilm comprises SiOC.
 3. The device as claimed in claim 1, wherein thechemical vapor deposition insulating film has a dielectric constant lessthan about 3.5.
 4. The device as claimed in claim 1, wherein thechemical vapor deposition insulating film is formed to have a thicknessmore than about 1 μm between the first electrode and the organicelectroluminescent layer.
 5. The device as claimed in claim 1, whereinthe opening portion of the chemical vapor deposition insulating film hasa tapered shape, and the second electrode has a stripe shape and crossesthe first electrode.
 6. The device as claimed in claim 5, wherein thechemical vapor deposition insulating film is comprised of SiOC.
 7. Thedevice as claimed in claim 5, wherein the chemical vapor depositioninsulating film has a dielectric constant less than about 3.5.
 8. Thedevice as claimed in claim 5, wherein the chemical vapor depositioninsulating film has a thickness more than about 1 μm between the firstelectrode and the organic electroluminescent layer.